Tube elongating apparatus and method



July 2, 1935. I A. P. DIESCHER TUBE ELONGATING APPARATUS AND METHOD Filed May 22, 1933 5 Sheets-Sheet l Eb N H l-m INVENTOR.

BY M WITNESSES v July 2, 1935. A. P. DIESCHER TUBE ELONGATING APPARATUS AND METHOD Filed May 22, 1933 5 Sheets-Sheet 2 INVEN TOR.

WITNESSES M ATTORNEYS.

y A. P. DHESCHER 2,006,336

TUBE ELONGATING APPARATUS AND METHOD Filed May 22, 1933 5 Sheets-Sheet 3 IN VENTOR.

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July 2, 19.35. A. P. DEESCHER 2306,3136

TUBE ELONGATING APPARATUS AND METHOD Filed May 22. 1935 5 Sheets-Sheet 4 W/TNESSES A T TORNEYS.

July 2, 1935. A. P. DIESCHER TUBE ELONGATING APPARATUS AND METHOD I Filed May 22, 1933 5 Sheets-Sheet 5 7 1w 'EXTOR.

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- Patented July 2, 1935 I I UNITED STATES PATENT OFFICE TUBE ELONGATING APPARATUS AND METHOD August P. Diescher, Pittsburgh, Pa., assignor to Diescher Tube Mills, Inc., Pittsburgh, Pa., a corporation of Delaware Application May 22, 1933, Serial No. 672,250

. 16 Claims. (Cl. 8013) My invention relates to the making of tubes, plying the mill with a succeeding blank after a a'nd more particularly to methods and apparatus cross-rolling operation has been completed is for cross-rolling tubular blanks on mandrels. ea y r ed- I In the operation of cross-rolling tubular The mandrel and the tubular blank are fed blanks on mandrels to reduce wall thickness and simultaneously into the cross-rolls by means of 6 elongate, and especially when the tubes are of a mandrel carriage for rotatably supporting the large diameter, the relatively thin hot walls of trailing end of the mandrel and a pusher mechthe tubes may be damaged by the weight of the anlsm movable with the mandrel carriage for mandrels, particularly if the mandrels are pern ing the trailing e of the tubular blankmitted to be delivered with the tube from the 'I'he mandrel carriage is motor driven and its 10 mill on to a delivery table unsupported otherwise speed is adjustable with respect to the longituthan by the tube, Furthermore,'the inertia of dinal movement of the tubular blank through the el y heavy mandrel must be overcome the cross-rolls after the pusher mechanism is by the mill when the latter engages the tubular disengaged from the tubular blank.

blank with the mandrel enclosed therein. The construction and operation of an ap- 16 In accordance with the present invention I proved apparatus embodying the apparatus feaprovide that the mandrel on which tubular tures and for practicing the method of my inblanks are cross-rolled does not pass entirely vention will be described in connection with the through the elongator mill to be delivered with accompanying drawings, in which Figfl is a the tube on to the delivery table but is retracted plan view of-feed tables and associated appa- 20 through the mill after the cross-rolling operaratus according to the invention, a cross-roll tion has been completed; and before the mandrel mill being shown diagrammatically in connecwith the tube thereon enters the cross-rolls it tion therewith; Fig. 2 is a side elevation of one is rotated at a speed which may be slightly less of the feed tables of Fig. 1 on an enlarged scale,

than that which will be imparted to it by the and showing also the table supporting struc- 25 cross-rolls, but which is suflicient substantially ture; Fig. 3 is an enlarged plan view of the to relieve the cross-rolls of the burden of overcross-roll mill and the delivery table; Fig. 4 is coming the inertia of the mandrel. In addian enlarged side elevation of the delivery table, tion, the rotation of the mandrel may rotate the a portion of the cross-roll mill being shown ditubular blank before it enters between the crossagrammatically; Fig. 5 is a vertical section of 30 rolls, but regardless of whether the tubular blank the mandrel-stripping mechanism; Fig. 6 is a is rotated before it enters the mill, the rotating plan view of the same; Fig. 7 is an enlarged elemandrel will aid in overcoming the inertia ofvation of a portion of a tubular blank and a the tubular blank since themandrel will be romandrel therefor and certain associated appatating in the interior of the blank when its ratus; Fig. 8 is an enlarged elevation of a 35 exterior is engaged by the cross-rolls. sprocket and certain cooperating apparatus;

In order that the mandrel, driven at a lower Fig. 9 is a transverse vertical sectional view speed by its driving mechanism, may rotate freely taken on line IX-IX of Fig. 7; Fig. 10 is an at the speed at which it may be actuated by the enlarged vertical section of the feed tables and cross-rolls, it is driven by mechanism including a supporting frame taken on line XX of Fig. 1, 40 one-way clutch which permits the mandrel to the pushing mechanism for the billets being rotate faster than it is v n y s driving omitted; Fig. 11 is an enlarged vertical section chanl m. of a mandrel carriage and certain of its asso- In order to facilitate the operation of the apciated parts; 2 is a transverse ti l paratus for producing seamless tubes, I provide Section taken on line XII XH of Fig 45 duplicate feed tables for supplying the crossrolls with tubular blanks and mandrels, which I are movable transversely for alignment alternately with the mill. In operation, while the mill is being supplied from one of the feed tables, the

13 is a similar view taken on line XHIXIII of Fig. 11; Fig. 14 is an enlarged side elevation of a portion of a mandrel carriage and certain related parts; Fig. 15 is a transverse vertical secother 'feed table is outv of alignment with the tional View of the feed table; 16 is a Side f mill and is being provided with a tubular blank elevation of a portion of a d table chain. and the mandrel is partially threaded thereportions of'a mandrel and of a tubular blank through. By placing the feed tables in alignbeing supported thereby; and Fig. 1'1 is an enment with the mill alternately, the delay in suplarged vertical ,section illustrating the gate mechanism for controlling the destination of tubular blanks.

Referring to the drawings, the cross-rolling mill I may, for example, be an elongating mill such as that shown and described in Patent No. 1,870,209, to S. E. Diescher, granted August 2, 1932. The mill comprises a pair of cross-rolls 2 and 3 the axes of which are inclined to each other and to the pass-line or axis of a tubular blank passing through the mill. The elongator is also provided with vertical discs 4 and 5 that rotate about axes at right angles to the pass-line to engage the blank between the crossrolls.

The elongator is supplied with tubular blanks to be treated therein by means of feed tables carried by a transversely movable frame 6 having conveying tables 1 and 8 upon'opposite sides thereof. The completed tubes are received by a delivery table 9 that is divided in two sections that are separated by a gear stand |0 from which the cross-rolls 2 and 3 are driven by means of spindles Referring particularly to Figs. 1, 2 and 10, the feed table carrying frame 6 is provided with rollers |3 for operation upon rails |4, whereby the feed tables may be shifted laterally from one operative position to another. The rails H are supported upon a framework I5, the elevation ofdrel carriage 26 provided with wheels 21 that roll upon rails 28 on the frame 6,,the mandrel carriage being connected to the chain 2| for longitudinal movement therewith. Certain of the links 29 of the chain 2| adjacent the mandrel carriage 26 carry mandrel supporting rollers 30 having axes parallel to the axis of a mandrel supported thereon, and other links carry mandrel and blank supporting rollers 3| that are arranged to rotate about axes at right angles to the axis of the mandrel thereon.

Each mandrel carriage 26 contains therein a movable frame 33, Figs. 11, 12 and 13, mounted for rocking or tilting movement on trunnions 34 in order to maintain its alignment with the mandrel connected thereto. The frame 33 carries a motor 35 the shaft of which is connected by gear mechanism 36, a one-way clutch 31, and a detachable coupling 38 to a hollow mandrel 39 that is preferably water-cooled and that is supported upon the rollers 3|] and 3 The coumechanism 43, and a shaft 44 having crank arms 45 that are connected to the framework 6 by means of links 46. As shown in Figs. 2, '1, 8, l5 and 16, therollers 30 and 3| are supported upon brackets 43 mounted on pairs of horizontal rods 49 having flanged wheels 50 thereon that roll on rails 5|. The chain 2| is connected'to the rods 49 for actuating the rollers 30 and 3| with the mandrel and with the tubular blank when the mandrel has been inserted therein.

A pusher mechanism for the tubular blank comprises a frame 52 that is connected to adjacent rods 49 between certain pairs of the lat ter, the frame 52 having slotted foot portions 53 at one end for permitting relative movement between the frame and the rod 49 extending through the slots when the frame 52 passes around the sprocket 23. Three frames 52 are shown by way of examples although any suitable member may be used.

Each frame 52 is provided with a series of vertical openings 54 in the top thereof for receiving the shank 55 of a curved pusher lug 56 for engaging the trailing end of the tubular blank when the mandrel has been threaded therethrough to the desired relative positions before feeding to the cross-rolls. The series of openings 54 provide that the lug 56 may be'adjusted for a number of positions in accordance with the length of the mandrel used or in accordance with the length of the portion of the mandrel projecting beyond the forward end of the tubular blank. A pin 51 looks the lug 56 in position and a cotter pin 58 prevents removal of the pin 51.

Each frame 52 is-provided with slotted foot portions 53 at one end thereof for permitting relative movement between the frame and the rod 49- extending through the slots 60 in order that the frame 52 may pass around the sprocket 23 and adjust itself to the thereby shortened distance between the rods 49 to which it is connected.

In the operation of the apparatus of my invention, it may be assumed that the feed table frame 6 is in the position illustrated in Fig. 1 with the feed table 20 in alignment with the crossroll mill I. It" may be assumed also that the aligned feed table 20 hasv been previously supplied with a tubular blank 63 and that a hollow mandrel 39 has been threaded therethrough to the extent indicated by dotted lines in this view. The chain 2| of the feed table 20 is actuated forwardly to complete the threading of the mandrel 39 through the tubular blank 63 to the desired advanced position before the blank and mandrel enter the cross-rolls of the mill, the blank being held in position by a disappearing limit stop 64 which permits the mandrel. to project therethrough. The lug 56 now engages the trailing end of the tubular blank 63.

The disappearing limit stop 64 is then dropped out of the longitudinal path of movement of the tubular blank 63 and the mandrel 39 therein is rotated by the motor 35 through the one-way clutch 31. The speed of rotation of the" mandrel is preferably slightly lessthan that at which it will .be driven by the cross-rolls when the tubular blank is engaged thereby. The motor 24 now drives the chain 2| forwardly and the blank and the mandrel are actuated into the mill by the lug 56 and mandrel carriage 26, respectively.

When the tubular blank is engaged by the cross-rolls of the mill the mandrel may rotateat the speed at which it is actuated by the mill, as is permitted by the one-way clutch, and the motor 35 may be stopped. The initial rotation of the mandrel may or may not rotate the tubularheavy mandrel has initially retarded the rotation of the tubular blank at the speed of the crossrolls.

When the tubular blank 63 and the mandrel 39 enter the mill the frame 52 carrying the block 56 is near the sprocket 23 and the lug 56 is disengaged from the tubular blank 63 after a short travel as the forward end of the frame 52 drops in its course around the sprocket 23. As soon as this disengagement occurs, the tubular blank is actuated by the cross-rolls and the mandrel by the chain 28. The rates of advance of the tubular blank and the mandrel may differ somewhat for reasons stated below. The relative positions of a frame 52 and the sprocket 23 when the chain H is at an intermediate portion of its travel are shown in Fig. 8. It will be noted that the slots (iii permit the frame and the rods so to assume their respective positions relative to the sprocket 23.

The rate of. advance of the mandrel between the cross-rolls during the cross-rolling operation may be regulated by the speed of the chain it to which the mandrel carriage 2b is connected. Ordinarily the rate or advance of the mandrel is a compromise between that of the portion of completed tube and the portion of the tubular blank that has not yet entered the cross-rolls. If the rate of advance of the mandrel under control of the chain 25 is faster than .that normally caused by the operation of the cross-rolls, it will assist the progress of the tubular blank through the mill, thereby increasing the rate of production of the mill. If, however, the speed of the chain is such that the mandrel advances more slowly than its normal rate, a shorter mandrel may be used, since the tube will be complete before the mandrel has advanced to the position it would occupy if it were not retarded.

When the tube is completed, the chain 2i is stopped and the tube upon the mandrel occupies a position on rollers 65 of the delivery table 9 which are adapted to be driven by means of a motor 66 and gear mechanisms 6i and til connected thereto. A portion of the mandrel projects on the delivery side of the mill. in order to retract the mandrel 39 through the cross-rolls it is usually necessary to employ mechanical means for preventing" the return movement of the completed tube, and a convenient mechanism for this purpose is illustrated in Figs. and 6.

The mandrel-stripping mechanism $9 provided for this purpose comprises horizontal arms it which support fluid pressure cylinders it that operate piston rods it to cause oppositely disposed curved gripping jaws i l to clamp the completed tube upon oppositrsides thereof, whereupon the chain 25 may be actuated in the opposite direction to return the mandrel carrime 2t and the mandrel 39 connected thereto to their inoperative positions which correspond to the positions occupied by the carriage 2t and inandrei 39 of the feed mechanism i9, Fig. 1, which is not in alignment with the mill l The completed tube is then released by the mandrel-stripping mechanism 69 and is con-- veyed by the rollers 65 through a suitable passageway in the gear stand IE to similar rollers 65 of a second section of the delivery table, these rollers being actuated by a motor 16 and gear mechanisms 11 and 18 connected thereto. The completed tube is then transferred from the delivery table 9 by means of a throw-outtmechanism 19 driven by a motor 80, and which transfers the tube to skids 8| whereby it may be transferred to any suitable location foreooling, or storage, or further processing.

In the meantime, while the feed tables are in their illustrated position and a tubular blank is being supplied by the feed table 29 to the crossroll mill i in the manner described above, the feed table is is being supplied with a tubular blank for the succeeding operation. A tubular blank 63,

, which may be supplied from a furnace or other suitable means for heating blanks, is illustrated as moving upon skids t2 toward the conveying table '5'. A gate 83, certain of the details of which are shown in Fig. 17, comprises arms it that are raised by a fluid pressure cylinder 85 to their uppermost positions, as indicated by dotted lines, Fig. 17, in which case the tubular blanket will drop into the grooves of rollers 86 of the conveying table l which are driven by means of a motor ti and gear mechanisms tit and 89 connected thereto.

When the tubular blank reaches the forward end of the conveying table 7:, it is transferred from the rollers at to skids tit by means of a transfer or throw-out=mechanism til similar to throwout mechanism it and comprising a series oi rotatable triangular members tit, one of which is shown in Fig. 15. The throw-out mechanism 98 is actuated by a motor 923. The tubular blank is deposited by the skids Qt upon rollers 30 of the chain iii of the feed table it], which is thus supplied with a blank.

The chain 211 of the feed table it? with a tubular blank thereon is then actuated to advance its mandrel carriage 2d and the mandrel 39 carried thereby to thread the mandrel into the tubular blank to substantially the relative position corresponding to that occupied by the tubular blank 63 and mandrel fill oi the feed table it, as illustrated in Fig. l. The tubular blank is prevented from moving forwardly by the disappearing limit stop (56. The mandrel is left in this intermediate position in order that it may not interfere with the lateral movement of the carrying frame- 5 which must occur in order to place the teed table it in alignment with the mill.

The frame it is then shifted laterally by means of the fluid pressure cylinder 32 and rack and pinion mechanism (133 and associated mechanism until the teed table is, which has just been supplied with a tubular blank, is in alignment with the mill and the feed table it? which has last supplied the mill is in a position adjacent the conveying table 8 that corresponds to that in which the feed table it? is illustrated with respect to the conveying table ll.

The operation of supplying the iced table it with a tubular blank by means of the conveying table 8 corresponds in every respect to that de-.

scribed for the conveying table i except that the gate t3 will be actuated to its lowermost posi tion in which the arms til bridge the gaps between the skids E32 and skids 95, extending over the rollers 8d of the table l. The skids 95 convey the tubular blank to the rollers d6 of the convey ing table 8. The blank is transferred from the forward end of table a by a throw-out mechanism $571 to skids 9b which conduct it to rollers 3 of the feed table it). i

The cycle of operations that has previously been described is then repeated. The alternation of the feed tables in one or the other of their positions is continued throughout the operation of the apparatus, the feed table that is not supplying the mill being provided with a tubular blank in readiness for the succeeding elongating operation and the mandrel being placed in position therein.

In case a mandrel becomes so highly heated as to require cooling before further use, it may be detached for. replacement by a cooler mandrel while its carriage is at its extreme position to the left by the operation of the detachable coupling by means of the lever 40. The frame 33 of the mandrel carriage will be retained in substantially the vertical position it occupies when a mandrel is connected thereto by means of a wheel 98 carried by the frame and which, when the carriage 26 is in its rearmost position, occupies a position between two horizontal guide plates 09 secured to a stationary post I00. The vertical positions of the guide plates 99 are adjusted by means of a hand wheel IM and a screw-threaded shaft I02.

The vertical positions of the trunnions 34 are also adjustable by means of a hand wheel I04 on a shaft that is geared to screw-threaded shafts I05 which carry the bearings for the trunnions. Proper vertical adjustment to insure alignment of the mandrel may be secured by this means.

By reference to Figs. 2 and 16 it will be noted that the'forward portions I06 of the rails ii for supporting the rollers 50 of each chain 2I are at a lower level than the remaining portions, and that the difference in levels is suflicient to compensate for the difference in diameters of the mandrels and tubular blanks 63 in order that the mandrels may be easily and conveniently threaded through the tubular blanks when the mandrel carriages and mandrels are actuated forwardly. It will be understood also that the difference in track level enables therollers 3| to support either the mandrel or the tubular blank, as the case may be. 7

A guard rail I08, Fig. 16, positively retains the wheels 50 on the inclined portion I08 of the rails 5i. The forward ends of the rail portions I06 are bent to extend concentrically with the sprocket 23. The other ends of the rails 5| are similarly curved around the axis of the sprocket 22-.

The provision of the mandrel supporting rollers 30 on each of the chains 2| enables the trailing end of the mandrel to be partially supported for rotation thereon after it has been actuated forwardly until the supporting rollers II have passed down the inclined portion of the rails SI and out of engagement therewith. The rollers 3| have axes at right angles to rollers III whereby they readily pass under the stationary tubular blank.

While the operation of the mandrel-stripping mechanism has been described as including the gripping or clamping of the completed tube, the tube clamping Jaws of the mechanism may also serve as an abutment for the tube while the mandrel is withdrawn. In such case, the laws 14 are closed loosely around the mandrel 'at the trailing end of the tube to prevent the return of the tube while permitting the mandrel to move freely.

The mandrel-stripping mechanism 00 may be adjusted for tubes of different diameters by suitably shifting the positions of the cylinders I2 toward or away from the outer ends of the arms II. Such adjustment is made by'loosening a nut I09 on a screw-threaded shaft H0 and rotating the latter by means of its square outer end.

The apparatus of my invention possesses a number of advantages that will be appreciated by those skilled in the art of construction and operation of cross-rolling apparatus, such, for example, as the provision of duplicate feed tables and asso ciated apparatus whereby upon the completion of an elongating operation another mandrel and tubular blank may be substantially in readiness for the succeeding operation. Alternate operation also permits the mandrels to cool or to be cooled by applying water during the intervals between operations, whereby they may remain in service throughout relatively long periods.

I The relatively heavy mandrel is positively rotated before it enters the cross-rolls of the mill, and it is not necessary for the latter to overcome the inertia of the mandrels. Furthermore, the rotation of the mandrel within the tubular blank assists the mill in overcoming the inertia of the tubular blank whether or not the latter is actually rotated by the mandrel. The provision of the one-way clutch connection between the motor and the mandrel driven thereby permits the latter to rotate faster than the speed of the motor, whereby the progress of the mill is not retarded.

The rate of advance of the mandrel into the cross-roll mill may be regulated as desired, whereby the mandrel may expedite the passage of the tubular blank through the mill or, if it is so desired, the rate of advance of the mandrel may be slower than that at which it is normally actuated by the mill, in which case a shorter mandrel may be employed.

I claim:

1. A feed table for cross-rolling mills, comprising mechanisms for advancing a mandrel and -a tubular blank thereon into the mill, and means connected to the mandrel for positively rotating it until the tubular blank is engaged by the mill and for permitting said mandrel when rotated by the mill and while connected to said rotating me m to rotate at a speed greater than the s ed of the rotating means.

2. The combination with a cross-rolling mill, of means for supplying tubular blanks to the mill comprising two parallel feed tables from which tubular blanks are fed longitudinally into the mill, means for moving said feed tables transversely to position them alternately in alignment with the mill, and means for supplying a tubular blank to each of said feed tables while it is out of alignment with said cross-rolls.

3. The combination with a cross-rolling mill, of means for supplying tubular blanks to the mill comprising a transversely shiftable support, two parallel feed tables carried by said support, means for moving said support to position said feed tables alternately in alignment with the mill, means for supplying tubular blanks to said feed tables alternately when in position out of alignment with the mill, and means for advancing the tubular blanks from the aligned table into the mill.

4. The combination with a cross-rolling'mill, of means for supplying tubular blanks to the mill comprising a transversely shiftable support,

. two parallel feed tables carried by said support,

two conveying tables for tubular blanks one on each side of said support, means for moving said support to position said feed tables alternately in alignment with the mill, means for transferring tubular blanks alternately from said conveying tables to the feed table which is in position out of alignment with the mill, and means associated transversely to position them alternately in alignment with the mill, means for supplying tubular blanks to the feed tables alternately when in position out of alignment with the mill, a mandrel 6. The combination with a cross-rolling mill, of

means for supplying tubular blanks with a contained mandrel to the mill comprising a transversely shiftable support, two parallel feed tables carried by said support, means for moving said support to position said feed tables alternately in alignment with the mill, means for supplying tubular blanks to the feed tables alternately when in position out of alignment with the mill, a mandrel carriage associated with each feed table, and means for moving the mandrel carriage of each feed table to advance a mandrel into the blank positioned on the table while the table is out of alignment with the mill and for advancing the blank and mandrel into the mill when the table has been positioned in alignment with the mill.

'7. The combination with a cross-rolling mill, of means for supplying tubular blanks with a contained mandrel to the mill comprising two parallel feed tables, means for moving said feed tables transversely to position them alternately in alignment with the mill, means for supplying tubular blanks to the feed tables alternately when in position out of alignment with the mill, and a mandrel on each feed table, each feed table being provided with means for advancing its mandrel into a blank positioned on the table and for advancing the blank and the mandrel into the mill and for retracting the mandrel through the mill after the blank has passed therethrough.

8. The combination with a cross-rolling mill, of means for supplying tubular blanks to the mill comprising mechanism for advancing a mandrel and a tubular blank thereon longitudinally into the mill and including means connected to the mandrel for positively rotating it while it is being thus advanced, said mechanism comprising means for permitting the mandrel to rotate faster than the driving means therefor.

9. The combination with a cross-rolling mill, of means for supplying tubular blanks to the mill comprising a feed table, having means movable longitudinally thereof to advance a mandrel and a tubular blank thereon into the mill, and having a motor and a one-way driving connection to the mandrel for rotating the latter prior to its entering the mill- 10. A feed table for cross-rolling mills, comprising reciprocable means for supporting a mandrel and a tubular blank and for advancing them into the mill, and a motor connected through a one-way clutch to themandrel for rotating the latter prior to its entering the mill, said means being operable also to retract the mandrel through the mill after the tubular blank has passed therethrough.

11. A feed table for cross-rolling mills, comprising a reciprocable chain having connected thereto means for supporting a mandrel and a tubular blank, and a mandrel carriage connected to move with said chain and comprising a motor and a one-way clutch for rotating the mandrel before it enters the mill, said clutch permitting said mandrel to be rotated by the mill faster than it is driven by said motor.

12. A feed table for cross-rolling mills comprising a mandrel carriage having a tiltable frame for adjusting its position to conform to that of a mandrel connected thereto when the carriage is in an operative position, and means for preventing tilting movement of said frame when the carriage is in an inoperative position.

13. A feed table for cross-rolling mills comprising a movable mandrel carriage having a frame for connection to a mandrel, said frame being tiltable about a horizontal axis to adjust its position to conform with that of said mandrel, and stationary means for restraining said frame from tilting movement when the carriage is in a retracted position relative to an associated cooperating cross-rolling mill.

14. A feed table for cross-rolling mills comprising a movable mandrel carriage having a frame for connection to a mandrel, said frame being tiltable about a horizontal axis to adjustits position to conform with that of said mandrel, means for adjusting the vertical position of said frame relative to said carriage, and means adjacent the path of movement of said carriage for preventing tilting movement of said frame when the carriage occupiesa certain position.

15. Apparatus for treating a tubular blank on a mandrel, comprising helically acting cross-rolls whereby the blank and contained mandrel are rotated and advanced longitudinally, and means connected to the mandrel for applying force to the mandrel acting in the direction of its longitudinal movement with the blank to cause it to advance at a rate in excess of its normal rate of advance with the blank under the action of the cross-rolls, and thereby increasing the rate of advance of the blank.

16. The method of treating tubular blanks, which comprises cross-rolling the blank on a mandrel between helically acting cross-rolls whereby the blank and contained mandrel are rotated and advanced longitudinally, and applying force directly to the mandrel in the direction of its longitudinal advance with the blank to cause is to advance at a rate in excess of its normal rate of advance with the blank under the action of the cross-rolls, and thereby increasing the rate of advance of the blank. 

